Process of preparing colored granular material



Patented my 19, 1932 1,867,661 4 UNITED STATES PATENT OFFICE JOHN V. FREEMAN, F IBELLEROSE, NEW YORK PROCESS OF PREPARING COLORED GRANULAR MATERIAL No Drawing. Application filed October 24, 1928. Serial No. 314,848. I

This invention relates to a process for pre will yield a product having a high degree of paring or treating colored granular material, uniformity and durability. such for example as granules of calcined sili- The invention consists in the process and cates, which may be used as a substitute for steps of the process which are herein de- 5 natural slate or other materials in the coating scribed according to a preferred manner of of composition roofing, shingles, etc. practicing the same, and the invention will be This application comprises a continuation particularly pointed out in the appended in part of my co-pending application Serial claims. No. 197,520,-filed June 8th, 1927. As is stated According to my invention, a treating proc- 10 in my said co-pending application, large ess is provided by which materials such as dumps or accumulations of fire clay formaabove described, or selected portions theretions now exist at various coal mines. These of, may be improved in color and color per accumulations contain a certain quantity of manency to such an extent as to be superior to coal and spontaneous combustion has accordthe materials heretofore used. This is pref- 5 ingly occurred therein, and with the oxidaerably accomplished by increasing the contion of the iron pyri-tes present, the fire clay tent of iron oxide. When the process is has been calcined and, under the prevailing applied to the calcined material of fire clay conditions of heat and pressure, has been dumps, for example, the resulting product'is formed into large clinker-like masses, largely of a bright red color, much more attractive color d r d b th i id than the red slate granules and other mate- Upon xaminati n it ha b n f und that rials heretofore used, yet the color is substanthis calcined fire clay has approximately the tlally uniform, and even after a prolonged exsame chemical composition and the same P Ilr t0 the atmospherewill not fade or physical structure as the natural slates now S a rce for the Iron oxide 1n this used in granular form a a, oating for, shintreatment, I may also use a material such as gl and th fi I f t, th h th used pickling liquor, a by-product from steel composition of this dump material varies, mllls Whlcl} would otherwise be 0f v y little of course, in different dumps and in difierent f Thls 1S substantlally a mural S0111- parts f th Same dump, t h f it, h t1on of ferrous sulphate. It w1ll be undera hi h t t f i id (F 0 d stood, however, that suitablesolutions for the so l i id (A1 0 hi h are l bl purpose may be provided artificially or otheringredients, and a much lower content of W158 m other combined Water than natural slates, and is, p l example lllustlal'jmg h a therefore, a superior material for the pur- 111 Whlch the Process of y "W y poses l t I be carrled out will now be described.

I have determined by successful tests that A Waste lf q y be 11ed P 11 this material which is now a waste product 18 denslty of 30 degrees Baume Wlth no and a source of expense for its disposal, may, acidity, 10.54 per cent 1ron and 6.04 per cent sulphur. The degree of concentration as 40 2:3 ::5Z% Z figgg s gli gg i g? the liquor is produced in the steel mills, or

as concentrated for economical shi ment ma formlty as to color, size. of granules and durap y be modified b eva oration or by addition of b1l1ty, and the product is thus well ad p ater. Gener ally the liquor produced at the as es for roofings and other P PQ mills is about 38 degrees to 40 degrees Baum as a substitute for more expensive materials and will be diluted to about 0. degrees This heretofore useddilution is chiefly for convenience in treat- It is therefore an object of this invention ing th aterial. 1 to provide a process for forming or treating The calcined fire clay material from the materials of the character above indicated, dump may be ground into granules and sized which process is economical and efiicient, and to the desired ultimate size and placed in a tank of such pickling liquor and allowed to stand and soak from 12 to 24 hours. It is then withdrawn and dried and preferably calcined in the following manner.

I have found that multiple hearth roasting furnaces of the type shown, for example, in the patent to Baird 1,669,925 of May 15, 1928, are satisfactory for use in carrying out this calcining process, although it will be understood that other types of multiple hearth furnaces of the same general class may be used. A furnace for example, having 11 hearths, including a top drying hearth, may be used. The material is preferably fed on to the drying hearth, upon which it is rabbled, until comparatively dry and from which it is gradually fed at a uniform rate into the furnace. As the material is rabbled successively over the various hearths down through the furnace, I find it desirable to gradually increase the temperature. The temperatures maintained on the various hearths may, for example, be in the neighborhood of the following:

At the top or drying hearth, approximately 300 F.,

At the first hearth within the furnace, 650 F.,

At the second hearth, 875 F.

Succeeding hearths may be heated at somewhat higher temperatures, to a maximum in the neighborhood of 1-050 F.

The desired temperatures in the furnace may be preferably maintained by firing with a good grade of oil distillate which avoids the introduction of any fuel and impurities which might alter the color produced.

An abundance of air, preferably preheated, is admitted to the furnace in such manner as to come into contact uniformly with the surfaces of all the granules. If the rabble arms of the furnace are rotated at a rate within the limits customary in the above mentioned class of furnaces, the material under treatment will be sufficiently rabbled on the various hearths so that all parts of the mass will be treated uniformly, yet in view of the form of raflfiing means used in the above mentioned type of furnace and since no large and heavy masses of the material will be accumulated at any one point, there will be very little tendency for the particles to become abraded.

Furthermore, when the temperatures are adually increased as above indicated, there will be no tendency for the particles to crack or become pulverized due to the heating and concurrent chemical actions. Accordingly the conditions prevailing in the furnace are such that the product will pass through the furnace and be discharged therefrom with substantially no powdering or abrasion of the granules or other alteration of the predetermined desired sizes thereof.

Products of various different, butpredetermined carefully graded sizes may accordingly be made. For example, ifthe product is to be used for ordinary shingle coating purposes, it may be crushed before treatment and the fines removed, leaving granules which will pass through a 10 mesh screen, but not through a 40 mesh screeni The same process may be applied with good results not only to the full red particles which constitute the major part ofthe dump or bank, but also to particles of other colors which occur, such as black, dark gray and greenish colors.

The iron of the waste pickling liquor or other treating liquid is very efficiently used according to this process and the same liquor may be re-used on further batches of clay material with the addition of fresh liquor as required.

With temperatures substantially as above referred to, a product Ofbright red color results. However, the color may be controlled by varying the temperatures. lVit-h temperatures higher than those above mentioned, the product may be given a reddish brown color. Various shades of color may be produced, depending upon the amount of the magnetic oxide which is formed, which in turn depends upon the temperatures applied and the length of time of calcination.

Apparently the gradual increasing of the temperature while the material is being slowly rabbled or otherwise agitated is essential or quite helpful in the formation of a uniform product, since such gradual heating with constant rabbling in the presence of air insures substantially uniform chemical and physical conditions throughout the mass of material.

The process of obtaining a uniform red color is applicable not only to the clay banks described, but to various materials of similar composition; such, for example, as natural slate (whether the original color be reddish or of the green and gray colors which are common), brickyard culls which are naturally of the same comparatively dull red color as the slate commonly used, broken bricks or tiles and other similar materials, natural or -artificial, all of which I include in the term ceramic materials. Where natural green slate is used, a bronze or somewhat reddish golden granule may be produced.

Also abright and uniform yellow product may be produced by applying the above described process at somewhat lower temperatures, not over 300 F., to certain granulated limestones. An example of a limestone which has been successfully treated for the production of yellow roofing granules showed the following percentage analysis: silica, 5.90; iron and aluminum oxides, 6.96; magnesia, 24.85; calcium, 59.32; undetermined, 2.86.

The loss on ignition of such a sample will average 45.30 per cent.

Instead of using Waste pickling liquor as above referred to, the process may be carried out usin solutions carrying in the neighborhood of% percent of ferrous sulphate, for example. However, the shade or depth of color may be modified at will, within rather Wide limits, by carrying the concentration of the solution so that more or less of the coloring ingredient is absorbed and the color may also be varied by varying the temperatures of calcination, as stated above.

The specific process described is particularly advantageous in that the solution is absorbed in the natural or artificial silicates with a high degree of uniformity so as to be permanently adhered to, or incorporated in the granules, the predetermined color becoming permanently set against variation even under extreme weather conditions.

An advantage in the roasting of the granules in a multiple hearth furnace as described is that there is very little abrasion. With the ordinary roasting processes it is necessary to re-screen the product to eliminate fines after re-calcination.

The roasting process of the present application may be carried out in such a way as to make re-screening unnecessary.

While the invention has been described in detail with respect to certain particular preferred examples which give satisfactory results, it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention, and it'is intended, therefore, in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

. 1. The herein described method of treating calcined clay granules to heighten and fix the color thereof, which comprises, soaking the granules in an iron solution to increase their iron content, drying the soaked granules, then feeding the granules in a substantially continuous stream throughout successive zones, subjecting the stream of granules to heat and increasing the temperature from each stream zone to the next succeeding stream zone, supplying air to the granules being heated, agitating the granules while being heated at the successive zones, and discharging the treated and color fixed granules from the last of the successive stream zones.

2. The herein described method of treating calcined clay granules to heighten and fix the color thereof, which comprises, soaking the granules in an iron solution to increase their iron content, drying the soaked granules, then feeding the granules in a substantially continuous stream throughout successive levels, subjecting the stream of granules to heat and mcreasing the temperature my name.

JOHN V. FREEMAN. 

